Air ignition system ammunition

ABSTRACT

There is herein disclosed a new and improved round of ammunition of the caseless type adapted for use in air-ignition system firearms and having a relatively narrow width shot start abutment shoulder and relatively short length rifling surface located at the rear of the projectile portion whereby a high degree of accuracy and optimum velocity are obtained.

United States Patent 42/1; l02/D1G. l, 56, 93, 38, 78

[56] References Cited UNITED STATES PATENTS 702,208 6/1902 Hayner 102/38 2,410,435 11/1946 Evans, .lr.. 102/38 3.096715 7/1963 Dufour 102/93 X 3,100,358 8/1963 Robinson, .Ir 42/78 3,398,684 8/1968 Kvaule 102/49.3

Primary Examiner-Samuel W. Engle Attorney-Harness, Dickey & Pierce ABSTRACT: There is herein disclosed a new and improved round of ammunition of the caseless type adapted for use in air-ignition system firearms and having a relatively narrow width shot start abutment shoulder and relatively short length rifling surface located at the rear of the projectile portion whereby a high degree of accuracy and optimum velocity are obtained.

AIR IGNITION SYSTEM AMMUNITION BACKGROUND AND SUMMARY OF INVENTION This invention represents an improvement in hot air ignition system caseless ammunition of the type disclosed in copending application, Ser. No. 473,556 filed July 7, I965. in the name of Jules E. Van Langenhoven for Air Operated Projectile Firing Apparatus and assigned to the same assignee as the present invention, the disclosure of which is incorporated herein by reference.

In general, an air-ignition system of the type to which this invention relates comprises a barrel bore through which a projectile is fired from a firing position in a firing chamber which enclosesat least a portion of the propellant and is connected to a source of hot compressed air. Shot-start controlling and barrel obturation means are provided to hold the ammunition in place in the firing chamber and to prevent escape of hot air or propellant gases around the ammunition and into the barrel bore. The ammunition is fired by delivering hot compressed air to the firing chamber and igniting the propellant by surface contact therewith. As the propellant burns, high-pressure propellant gases are produced which drive the projectile through the bore.

This invention relates to the problems of obtaining consistency in velocity and accuracy of the projectile. It has been determined that variations in velocity in the same typeof ammunition are related at least in part to the effect of shot-start parameters on ignition and burning characteristics. If the shotstart force is too small, the ammunition begins to move through the barrel before sufficient burning to obtain maximum energy release. It has also been determined that variations in accuracy are related at least in part to the location of the shot-start control means on the projectile and the relationship of the shot-start control means to rifiing means provided to impart a rotation to the projectile. The present invention involves discovery of the controlling parameters and provision of interrelated means for achieving an optimum relationship between the parameters affecting velocity and accuracy. The interrelated means comprise shot-start controlling means, barrel-obturating means, rifiing means, and antiwobble means.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a side elevational view of a round of caseless ammunition embodying the inventive concepts and shown in a firing position in an air-ignition gun;

FIG. 2 is an end view of the round of caseless ammunition shown in FIG. I; and

FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 1.

DETAILED DESCRIPTION The round of caseless ammunition comprises a generally cylindrical projectile portion 12, formed of lead or the like, and a generally cylindrical solid propellant portion 14 attached thereto. The outside diameter of the propellant portion may be equal to or slightly less than the outside diameter of the adjacent portion of the projectile. The ammunition is adapted to be placed in a firing position within ammunitionholding means 15 of an air-ignition gun, as shown in FIG. i, in alignment with a barrel bore 16 having rifiing groove means 18. A transverse shot-start control and sealing shoulder 20 connects the bore 16 to enlarged firing chamber means 21, 22. A breech means 24 having a valved hot air passage 26 closes and obturates the rear end of the firing chamber means as described in the aforementioned prior application.

Projectile l2 comprises a front or nose portion 30. an intermediate body portion 32, a rear body portion 34, and a tail portion 36. In the illustrative embodiment. nose portion 30 has a rounded peripheral side surface 38 and a flat front surface 40. A transverse shoulder 42 intersects the rounded peripheral side surface 40 and connects it to the intermediate body portion 32 which provides antiwobble means in the form of a cylindrical peripheral side surface or band 41 generally corresponding to the diameter of bore 16 so as to provide close guiding support for the projectile in the firing position and throughout the travel of the projectile through the bore. While the shoulder 42 may be varied in size and location, or even eliminated completely as necessary or desirable, the axial length of band 41 is of sufficient length to prevent wobble of the projectile in the bore.

A transverse shot-start control and sealing shoulder 44 connects front and intermediate body portions 30, 32 to the rear cylindrical body portion 34 and is axially located so as'to provide a relatively long length antiwobble band 41 and a relatively short length rifiing band 45. The difference in diameter between the rear portion and the front portion, i.e., the radial width of the shoulder 44, is such as to engage the correspond ing shoulder 20 in the firing chamber radially outwardly of the rifiing grooves and provide a seal and stop between the projectile and the gun in the firing position to prevent escape of hot compressed ignition air into the bore 16 and to prevent escape of propellant gases into the bore 16 until a predetermined minimum shot-start force is obtained in the firing chamber 22. The radial width of the shoulder 44 and the axial length of the rifling band 45 are also correlated to obtain the desired rifiing effect as the projectile moves through the barrel bore 16.

The reduced diameter tail portion 36 is integral with the body portion 34 and extends centrally rearwardly. The tail portion is pierced and outwardly flared by a suitable tool to form a triangularly shaped recess 46 and three semicylindrical ears 48, 50, 52. The depth of the recess 46 is approximately equal to the length of the post and the peripheral side surface 54 of the post tapers rearwardly outwardly so that the radial width of the ear portions exceeds the radius of the portion of the post at the rear body portion thereby to provide movement restraining means preventing axial displacement of the propellant on the post.

The illustrative round of ammunition is of .22-caliber 29 grain size having a design velocity of l,l50 f.p.s. Particularly good results have been obtained when the axial length of the rifiing band on the rear body portion is relatively short, i.e., substantially less than the overall length of the front portions 30, 32 and even substantially less than the length of intermediate antiwobble band on portion 32. In the presently preferred form of the invention, the axial length of the rifling band on the rear body portion is approximately 0.068 inch whereas the length of the antiwobble band is approximately 0.120 inch and the length of the nose portion is also approximately 0.120 inch. Tests indicate that when the rifiing band length is shorter, the shot-start force is reduced beyond the lower limit required to obtain the desired velocity. If the length is longer, the rifiing effect causes undesirable deviations in accuracy. The tests indicate that a length less than 0.050 inch or greater than 0. l 30 inch are unsatisfactory.

The diameter of the rear body portion 34 is held between approximately 0224-0225 inch and the diameter of the intermediate body portion 32 is held between approximately 0.2 l 7-0.218 inch so that the radial width of the shoulder 44 is approximately 0.0035 inch. It appears that the width of the shot-start control and sealing shoulder 44 must be within 20.0015 inch of the presently preferred 0.0035 inch to achieve optimum results.

Tests with .22-caliber ammunition indicate that the length of the front portion, and hence the mass, may be varied without significant deviation in the results so that the preferred axial length of the rear portion 34 and the preferred radial length of the shot-start and sealing shoulder 44 appear to be independent of the overall length or mass of the projectile.

Rear shoulder 44 is adapted to abuttlngly engage shoulder 20 in the firearm in the firing position to hold the round of ammunition in the firing position until the propellant has been ignited and a predetermined shot-start force is built up in the firing chamber by the propellant gases. Tests indicate that shotstart forces of approximately between 40 and 65 psi. (50 p.s.i. presently preferred) will enable the buildup of intermediate propellant gas pressures of approximately between 4,000 and 5,000 psi. which will result in consistent obtaining of the desired 1,150 f.p.s. velocity. The shoulder 44 also serves as a seal to prevent escape of the hot compressed ignition air prior to propellant ignition and as an obturator for propellant gases for the front of the firing chamber.

The relatively short axial length rifiing band on the rear body portion 34 provides rifiing means engageable with and engravable by the rifiing grooves 18 in the bore of the firearm to impart rotational movement to the projectile. The depth of the rifling grooves are maintained at 0.220-0221 inch so that there will be approximately 0.002-inch overlap of the shoulder 44 on shoulder 20 to cover the rifiing grooves in the starting position. When the shot'start force is reached, and the projectile begins to move in the bore, the rifiing band is squeezed into the bore with ridge portions being formed in the rifiing grooves and groove portions being formed therebetween. By providing a narrow width shot-start shoulder and a short length rifiing surface, surprisingly better results have been achieved with regard to standardization of projectile velocities and flight patterns.

Furthermore, better results are achieved with the present invention than in the prior art by providing substantially full engagement between the antiwobble band 4l on the front of the projectile and the barrel in the firing position. For this purpose the diameter of the barrel bore and the diameter of the antiwobble band 41 are held to the same dimensions, i.e., 0.217- 0.218 inch in the presently preferred embodiment. However, the end of the barrel bore adjacent and forward of the shoulder 20 may be provided with a slight taper to facilitate positioning of the round in the firing position. A diameter at the shoulder of 0.2 1 910.0005 is satisfactory.

The propellant portion may be molded directly onto the rear of the projectile about the post. In the illustrative embodiment, the propellant has a diameter of approximately equal to or slightly less than the body portion 34 and a length of approximately 0.300 inch.

Since the illustrative embodiment of the invention is susceptible to modification and change without changing the inventive concepts, it is intended that the appended claims be construed to cover alternative embodiments except so far as limited by the prior art.

We claim:

1. The combination of an air-ignition gun or the like and a round of caseless ammunition in a firing position therein comprising:

barrel bore means for guiding a projectile from the gun,

firing chamber means aligned with and rearwardly adjacent to said bore means and being enlarged relative thereto and having an axially extending chamber enclosing wall next adjacent said bore means,

a shot-start-controlling and barrel-obturating transverse shoulder means connecting said bore means to said wall,

rifling groove means in said bore means extending forwardly from said shoulder means and opening rearwardly into said firing chamber means through said transverse shoulder means and terminating radially inwardly of said wall with portions of said shoulder means being located radially outwardly between said rifiing groove means and said wall,

a round of easeless ammunition having a generally cylindrical overall peripheral configuration mounted in a firing position in the gun,

said round comprising a generally cylindrical full solid onethan said nose portion and approximately e ual in diameter to the diameter of said ore means an mounted in said bore means forward of said shoulder means in close sliding engagement therewith,

rifiing band means provided by a rear body portion of said projectile and having a diameter larger than the diameter of said intermediate body portion and larger than the diameter of said bore means and said rifiing groove means and smaller in diameter than said wall of said firing chamber means and being mounted in said firing chamber means rearwardly of said shoulder means in radially inwardly spaced relationship to said wall,

said rear body portion being rearwardly terminated by a transverse rearwardly facing closed end surface, said rear body portion having an axially extending generally cylindrical peripheral surface of generally uniform diameter extending rearwardly from said intermediate body portion and terminating at the rear end of said projectile at said end surface,

a transverse shot-start-controlling shoulder connecting said intermediate body portion to said rear body portion and sealing and restrainingly engaging said shoulder means about and radially beyond said bore means and said rifiing groove means to prevent axial forward movement of said projectile portion until a predetermined shot-start force is generated by propellant gases in said firing chamber means and to prevent flow of gases from said firing chamber means into said bore means, and

said round further comprising a solid propellant attached to the rear of said projectile and having a generally cylindrical outer peripheral surface extending rearwardly from said transverse rearwardly facing closed end surface on said projectile. the generally cylindrical outer peripheral surface of said propellant being located rearwardly of said rear body portion of said projectile and being unenclosed by said projectile, and the diameter of said propellant being less than the diameter of said wall and located in radially inwardly spaced relationship relative thereto.

2. The invention as defined in claim 1 and wherein the nominal diameters of said bore means and said antiwobble band means are the same and the tolerance is approximately 10.00] inch.

3. The invention as defined in claim 1 and the ammunition being of .22-caliber size and wherein:

the diameter ofsaid bore means and the diameter of said antiwobble band means being between 0.217 and 0.218 inch.

4. The invention as defined in claim 1 and the ammunition being of .22-caliber size and wherein:

the axial length of said rifiing band means is approximately 0.068 inch with a tolerance of10.0l5 inch.

5v The invention as defined in claim 4 and wherein:

the shoulder having a radial width of 00035100005 inch.

6. The invention as defined in claim 5 and wherein:

the radial depth of said rifiing groove means is approximately 0.004 inch.

7. The invention as defined in claim 4 and wherein:

the axial length of said antiwobble bond means being at least 0. l 20 inch. 

1. The cOmbination of an air-ignition gun or the like and a round of caseless ammunition in a firing position therein comprising: barrel bore means for guiding a projectile from the gun, firing chamber means aligned with and rearwardly adjacent to said bore means and being enlarged relative thereto and having an axially extending chamber enclosing wall next adjacent said bore means, a shot-start-controlling and barrel-obturating transverse shoulder means connecting said bore means to said wall, rifling groove means in said bore means extending forwardly from said shoulder means and opening rearwardly into said firing chamber means through said transverse shoulder means and terminating radially inwardly of said wall with portions of said shoulder means being located radially outwardly between said rifling groove means and said wall, a round of caseless ammunition having a generally cylindrical overall peripheral configuration mounted in a firing position in the gun, said round comprising a generally cylindrical full solid onepiece projectile, a front nose portion of said projectile being of smaller diameter than said bore means and mounted in said bore means forward of said shoulder means, antiwobble band means provided by an intermediate body portion of said projectile and being of larger diameter than said nose portion and approximately equal in diameter to the diameter of said bore means and mounted in said bore means forward of said shoulder means in close sliding engagement therewith, rifling band means provided by a rear body portion of said projectile and having a diameter larger than the diameter of said intermediate body portion and larger than the diameter of said bore means and said rifling groove means and smaller in diameter than said wall of said firing chamber means and being mounted in said firing chamber means rearwardly of said shoulder means in radially inwardly spaced relationship to said wall, said rear body portion being rearwardly terminated by a transverse rearwardly facing closed end surface, said rear body portion having an axially extending generally cylindrical peripheral surface of generally uniform diameter extending rearwardly from said intermediate body portion and terminating at the rear end of said projectile at said end surface, a transverse shot-start-controlling shoulder connecting said intermediate body portion to said rear body portion and sealing and restrainingly engaging said shoulder means about and radially beyond said bore means and said rifling groove means to prevent axial forward movement of said projectile portion until a predetermined shot-start force is generated by propellant gases in said firing chamber means and to prevent flow of gases from said firing chamber means into said bore means, and said round further comprising a solid propellant attached to the rear of said projectile and having a generally cylindrical outer peripheral surface extending rearwardly from said transverse rearwardly facing closed end surface on said projectile, the generally cylindrical outer peripheral surface of said propellant being located rearwardly of said rear body portion of said projectile and being unenclosed by said projectile, and the diameter of said propellant being less than the diameter of said wall and located in radially inwardly spaced relationship relative thereto.
 2. The invention as defined in claim 1 and wherein the nominal diameters of said bore means and said antiwobble band means are the same and the tolerance is approximately + or - 0.001 inch.
 3. The invention as defined in claim 1 and the ammunition being of .22-caliber size and wherein: the diameter of said bore means and the diameter of said antiwobble band means being between 0.217 and 0.218 inch.
 4. The invention as defined in claim 1 and the ammunition being of .22-caliber size and wherein: the axial length of said rifling band means is approximately 0.068 inch with a tolerance of + or - 0.015 inch.
 5. The invention as defined in claim 4 and wherein: the shoulder having a radial width of 0.0035 + or - 0.0005 inch.
 6. The invention as defined in claim 5 and wherein: the radial depth of said rifling groove means is approximately 0.004 inch.
 7. The invention as defined in claim 4 and wherein: the axial length of said antiwobble bond means being at least 0.120 inch. 